Sexually transmitted infections (STI), including human immunodeficiency virus (HIV), pose significant health risks. About half of the new HIV infections in the US are among people under age 25 years with the majority infected through sexual behavior. About one in three new diagnoses with HIV/AIDS are attributed to heterosexual transmission. Men who have sex with women play a major role in HIV transmission to women who can also pass it on to offspring. Consistent and correct use of condoms can be a highly effective method of preventing the transmission of HIV and many STIs. Yet, studies show that problems with condom use are common and that these problems pose a barrier to consistent and complete condom use. This project aims to advance our understanding of, among other factors, the role of cognitive and affective processes and condom application skills in explaining problems with condom use in young, heterosexual adult men. A multi-method approach - consisting of two studies and involving questionnaires, observational, and psychophysiological methods - will be used in conjunction with a skill-based intervention. The knowledge gained from the proposed research can be used to inform the development of innovative, more effective, and targeted intervention and education strategies tailored to the needs of individuals who have trouble using condoms effectively. PUBLIC HEALTH RELEVANCE: Sexually transmitted infections (STI), including human immunodeficiency virus (HIV), pose significant health risks. Consistent and correct use of condoms can be a highly effective method of preventing the transmission of HIV and many STIs, yet studies show that problems with condom use are common. This project is one of the first to examine under controlled conditions the role of cognitive and affective factors and condom skills in explaining condom use problems in young, heterosexual adult men.